1. Field of the Invention
The present invention relates to an image processing apparatus, an image forming apparatus, an image processing method and a recording medium, which have a function to erase a non-image area.
2. Description of Related Art
An image processing apparatus provided in a conventional image forming apparatus has a so-called non-image area erase function, which is to prevent toner transcription and the like in the non-image area by distinguishing an image area and a non-image area and by replacing a black pixel with a white pixel. The image forming apparatus described in JP-2002-84409A reads monochrome density and a luminance data of external light by performing sky shot, and confirms a luminance value of a foot of a peak including a maximum frequency value measured on the histogram thereof, when an image area is detected. Subsequently, as shown in FIG. 10, the higher luminance out of the confirmed luminance values is set as an external light level. Based on the external light level, environment where an image forming apparatus is installed is checked and the check result is displayed on display means. FIG. 11 shows a display example of a check result of environment where an image forming apparatus is installed, and sentences are displayed according to the Warning Level.
However, an image processing apparatus provided in a conventional image forming apparatus erases a non-image area by using the histogram based on monochrome density of external light. Thus, the image processing apparatus has never checked the environment in consideration of colors of external light. Therefore, it has been problematic that even an image forming apparatus compatible with colorization is not capable of accurately erasing a non-image area in a colored original manuscript according to a color of external light.
The present invention has been developed in consideration of this problem, and an object of the present invention is to provide an image processing apparatus, an image forming apparatus, an image processing method and a recording medium, which can erase a non-image area according to a color of external light.